24 research outputs found

    Development of a novel photocatalytic reactor for the treatment of polycyclic aromatic hydrocarbons.

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    Water pollution through the discharge of contaminated water into the environment has been a major problem, both to humans and aquatic life. These potential consequences mean that water pollution has therefore received major attention. In industry, a group of contaminants still facing challenges with regards to effective remediation are the polycyclic aromatic hydrocarbons (PAH) present in water. These PAHs impose significant risk due to their carcinogenic, mutagenic and teratogenic potential. 18 of these PAHs are classified as high priority by the Environmental Protection Agency (EPA) due to their toxic and harmful nature. This research investigated two remediation methods - coagulation-flocculation and photocatalysis - for the remediation of these 18 PAHs in water. In each remediation method investigated, preliminary works were first carried out on 3 PAHs (naphthalene, phenanthrene and fluorene) before then applying the method to the other 15 PAHs. The coagulation-flocculation remediation method was investigated because the literature review proved that it was an effective method in the adsorption of pollutants from water. Also in the investigation, powder and solubilized (in acetone) chitosan were used as an adsorbent to remove the PAHs in water. Results from this investigation showed little significance in the removal of PAHs with a removal efficiency of 15% attained for phenanthrene using powder chitosan (25 ppm) at 30 minutes contact time. An increase in contact time to 120 hours increased the removal efficiency to 88%. To attain sustainable removal from an industrial treatment point of view, a fast and effective remediation method is required. At 120 hours duration, this method is too slow, meaning that further investigation for a more rapid and effective method required. The photocatalysis remediation method was identified as an alternative. Investigation carried out using the photocatalytic remediation method involved the design and construction of a photocatalytic reactor. Preliminary work was first carried out in a constructed batch suspended photocatalytic reactor to investigate the photodegradation of naphthalene, phenantharene and fluorene, in order to confirm the photocatalytic ability of TiO2 to photodegrade PAH under the influence of UV light. A high removal efficiency of 99% was achieved, but with the limitation of needing to subsequently remove the TiO2. Due to the secondary treatment required to remove TiO2, an immobilized photocatalyst reactor was then investigated. Preliminary work was first carried out on a batch immobilized TiO2 coated photoreactor. This achieved significant results with 83% removal of naphthalene from water over 20 minutes. As a result of this investigation, this study then moved to focus on the design and construction of a flow-through photocatalytic reactor. The developed reactor included both an immobilized TiO2 photocatalyst and UV light radiation. In testing, the novel reactor achieved a high removal rate of 84% in the removal of naphthalene in water. Further investigation with the PAH present in synthesized sea water achieved a similarly high removal rate of 77%. This novel flow-through photocatalytic reactor therefore provides a solution to the challenge of effective removal of PAHs in water

    Sedimentos subaquáticos como fontes de bactérias anaeróbicas facultativas hidrocarbonoclásticas e produtoras de biossurfactantes

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    Doutoramento em Engenharia QuímicaActualmente são conhecidas poucas estirpes bacterianas capazes de produzir biossurfactantes (BSFs) em condições de microaerobiose ou anaerobiose. Estas bactérias têm um papel importante não só em processos naturais (ex. formação de biofilmes ou de hidratos de gás), como podem ter diversas aplicações biotecnológicas (ex. estratégias de biorremediação e aplicações industriais). As bactérias produtoras de BSFs em condições de limitação de oxigénio, com capacidade para degradar hidrocarbonetos são de particular interesse para estratégias de biorremediação de locais contaminados com hidrocarbonetos de petróleo (PHs) e na recuperação microbiana de petróleo (MEOR). Neste contexto, o objectivo deste trabalho foi o isolamento, identificação e a caracterização de bactérias anaeróbias ou anaeróbias facultativas produtoras de BSF e degradadoras de hidrocarbonetos (hidrocarbonoclásticas) na perspetiva da sua aplicação biotecnológica em condições de limitação de oxigénio. Foram escolhidos dois ambientes contaminados com PHs como potenciais fontes de bactérias hidrocarbonoclásticas produtoras de BSFs: vulcões de lama (MV) de mar profundo do Golfo de Cádis (Oceano Atlântico) e o sistema estuarino da Ria de Aveiro (Portugal). Foram preparadas culturas de enriquecimento com sedimentos subaquáticos recolhidos nestes dois habitats, como potenciais inóculos de bactérias anaeróbias facultativas. Um design experimental fatorial foi usado para testar o efeito do crude como fonte de carbono, e de nitrato e/ou sulfato, como aceitadores terminais de eletrões. De forma a melhor compreender a estrutura das comunidades bacterianas envolvidas na biodegradação de PHs nos MV do mar profundo procedeu-se à sequenciação do gene 16S rRNA das comunidades bacterianas de culturas de enriquecimento com sedimento de dois MVs, um activo e outro inactivo, e com ou sem adição de crude e/ou nitrato. Detetou-se uma diferenciação entre as comunidades dos dois MVs, independentemente dos suplementos a que as culturas foram expostas, sendo que Alphaproteobacteria e Bacilli predominaram nas culturas com sedimentos de MV activo e inactivo, respectivamente. De uma forma menos acentuada, tanto o nitrato como o crude afetaram a composição das comunidades bacterianas. Géneros de bactérias que só foram detectados nos ensaios com adição de crude (ex. Erythrobacteraceae no MV activo e Acidimicrobiale no MV inactivo) poderão ser usados como indicadores da presença de hidrocarbonetos de petróleo nestes habitats. A biodegradação de PHs nas culturas com crude foi avaliada por cromatografia gasosa acoplada a espectrometria de massa. De uma forma geral, as comunidades de culturas do MV activo foram capazes de degradar n-alcanos de tamanho inferior a C13 e compostos monoaromáticos, enquanto as comunidades do MV inactivo apresentaram a capacidade de metabolizar vários tipos de hidrocarbonetos aromáticos policíclicos. A presença de nitrato apenas afectou positivamente a biodegradação de alcanos, e não teve efeito ou foi mesmo inibitória da biodegradação de outros hidrocarbonetos. A partir de todas as culturas, com todos os tipos de sedimentos, dos MVs do Golfo de Cádis e do estuário da Ria de Aveiro, foi possível isolar-se um total de 13 isolados capazes de sobreviver exclusivamente com crude como fonte de carbono e produzir BSF em condições de aerobiose. Destas, apenas duas não foram capazes de produzir BSFs em anaerobiose. A sequenciação do gene 16S rRNA dos isolados permitiu identifica-los como pertencendo aos géneros Pseudomonas, Bacillus, Ochrobactrum, Brevundimonas, Psychrobacter, Staphylococcus, Marinobacter e Curtobacterium, a maioria dos quais não tinha ainda membros conhecidos como produtores de BSF em anaerobiose. Os resultados obtidos com este trabalho permitiram caracterizar melhor as comunidades envolvidas na degradação de PHs em MVs de mar profundo. Conseguiu-se ainda isolar e identificar estirpes, tanto de mar profundo como de ambiente estuarino, capazes de degradar PHs e produzir BSFs em condições de anaerobiose. Estas estirpes apresentam elevado potencial biotecnológico para aplicações como MEOR e biorremediação em ambientes com escassez de oxigénio.So far, only few bacterial strains are known to produce biosurfactants (BSFs) under microaerobic or anaerobic conditions. However, these bacteria are not only involved in important natural processes (e.g. biofilm and gas hydrates formations) but can also be used in several biotechnological applications (e.g. bioremediation strategies and industrial applications). Bacteria able to produce BSFs under oxygen-limiting conditions that are also able to degrade hydrocarbons, are of particular interest to bioremediation strategies of sites contaminated with petroleum hydrocarbons (PHs) and microbial enhanced oil recovery (MEOR) strategies. In this context, this work aims at isolating, identifying, and characterizing BSF-producing and hydrocarbon-degrading (hydrocarbonoclastic) bacteria grown under anaerobic conditions, which can be used in biotechnological applications under oxygen limitation. Two environments contaminated with PHs were chosen as potential sources of hydrocarbonoclastic BSF-producing bacteria: deep-sea mud volcanos from the Gulf of Cadiz (Atlantic Ocean), and the estuarine system of Ria de Aveiro (Portugal). Enrichment cultures were prepared using subaquatic sediments from both sites, as potential sources of facultative anaerobic bacteria. A factorial experimental design was used to test the effect of crude oil as carbon source, and nitrate and/or sulfate, as terminal electron acceptors. Aiming at better understanding the structure of bacterial communities involved in PHs biodegradation at deep-sea MVs, sequencing of the 16S rRNA gene was performed for bacterial communities from cultures containing sediments from two MVs, active and inactive, and with or without crude oil and/or nitrate. A distinction between the communities of MVs with different activity, independent of the supplements was observed. Alphaproteobacteria and Bacilli were the predominant classes found in enrichment cultures inoculated with active and inactive MVs sediments, respectively. In a minor scale, nitrate and crude oil additions also affected the composition of bacterial communities. Therefore, genera that only appeared in cultures with crude oil. (e.g. Erythrobacteraceae in active MV cultures and Acidimicrobiale in inactive MV cultures) can be used as biosensors of the presence of PHs in these habitats. Biodegradation of PHs in cultures containing crude oil was assessed by gas chromatography coupled with mass spectrometry. Overall, communities from active MV cultures were able to degrade n-alkanes below C13 and monoaromatic hydrocarbons, while communities from inactive MV cultures presented the ability to metabolize several types of polycyclic aromatic hydrocarbons. The presence of nitrate only had a positive effect on the biodegradation of alkanes, and had no effect or even an inhibitory effect on the biodegradation of other hydrocarbons. A total of 13 isolates able to survive on crude as carbon source and produce BSF under aerobic conditions were obtained from all cultures either from sediments of the Gulf of Cadiz MVs or the estuarine system of Ria de Aveiro. Only two isolates failed to produce BSF under anaerobiosis. Sequencing of 16S rRNA gene was used to establish the identification of isolates as Pseudomonas, Bacillus, Ochrobactrum, Brevundimonas, Psychrobacter, Staphylococcus, Marinobacter and Curtobacterium. Most of these genera had never been described as able to produce BSFs under anaerobic conditions. The results obtained in this work allowed to better characterize the deep-sea communities involved in PHs degradation, as well as, to identify strains from deep-sea and estuarine sediments able to degrade PHs and produce BSFs under anaerobic conditions. These bacteria present high biotechnological potential for applications in oxygen-limiting environments, such as, MEOR and bioremediation of environments contaminated with PHs

    Bioremediation of creosote-contaminated soil by microbial intervention..

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    Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2002.No abstract available

    Integrated physical-Fenton remediation of petroleum-contaminated soil using ethyl lactate as a green solvent

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    The huge amount of petroleum hydrocarbons contaminated sites is the heritage of a long history of fossil fuels usage. Reducing petroleum hydrocarbons levels in contaminated soils by Fenton reaction and with the aid of one or two agents such as solvents, surfactants, or vegetable oils has been studied in recent years, with successful reported results. Nonetheless, destruction of the aliphatic fraction of total petroleum hydrocarbon (TPH) by Fenton reaction has been studied to a lesser extent as compared to the aromatic fraction of TPH. Additionally, studies regarding the effect of humic acid (HA) on Fenton reaction reported contradictory results, and more research is necessary to clarify HA effects. Lastly, although achieving the highest efficiency is the main objective of soil remediation technologies, the environmental side effects of the applied processes should be considered as important as the efficiency. In light of these, the main aim of this project was to increase Fenton treatment efficiency by using an environmental friendly solvent, ethyl lactate (EL). The project objectives included determining optimum levels for the reagents of Fenton reaction and desorption process such as hydrogen peroxide (H2O2) and EL, identifying the kinetic of TPH desorption and destruction of petroleum hydrocarbons by Fenton reaction in addition to analysing the effects of EL on these processes. Through desorption tests, EL/water solution demonstrated great ability to increase the removal efficiency and desorption of sorbed TPH. Desorption by EL/water solution consisted of a very fast desorption stage followed by a slow stage. After 30 min of desorption, the removal efficiency of TPH increased from 63% to 81% for EL=25% and EL=100%, respectively. The initial desorption rate for 25% and 100% were 1.625 mg/min and 3.368 mg/min, respectively. The results of batch experiments indicated that EL%=10% was the optimum value for the EL-modified Fenton reaction. After 4 h, an increase in H2O2 concentration from 0.1 M to 2 M at L/S=2 and EL=25% increased the removal efficiency of TPH from 68.41% to 90.21%. HA addition up to 150 mg/l was also studied. For fraction 1, adding HA led to an increase in removal efficiency while for fraction 2, only HA=150mg/l had higher removal efficiency than the HA=0 case and for fraction 3, addition of HA in the studied range could not increase the removal efficiency. A good compatibility of zero-valent iron nanomaterial with H2O2 was proved. Laboratory column experiments were finally carried out to remove petroleum hydrocarbons from diesel-contaminated soil with EL to reproduce the conditions of in-situ treatment. The remaining diesel in soil decreased by increasing H2O2 molarity from 0.1 M to 0.5 M whereas a further increase to 2 M led to an increase in remaining diesel in soil. The stability of H2O2 in EL has been observed which signifies good potential for in-situ applications. Overall, the project has demonstrated the feasibility of EL-modified Fenton reaction for the remediation of petroleum-contaminated soil

    Integrated physical-Fenton remediation of petroleum-contaminated soil using ethyl lactate as a green solvent

    Get PDF
    The huge amount of petroleum hydrocarbons contaminated sites is the heritage of a long history of fossil fuels usage. Reducing petroleum hydrocarbons levels in contaminated soils by Fenton reaction and with the aid of one or two agents such as solvents, surfactants, or vegetable oils has been studied in recent years, with successful reported results. Nonetheless, destruction of the aliphatic fraction of total petroleum hydrocarbon (TPH) by Fenton reaction has been studied to a lesser extent as compared to the aromatic fraction of TPH. Additionally, studies regarding the effect of humic acid (HA) on Fenton reaction reported contradictory results, and more research is necessary to clarify HA effects. Lastly, although achieving the highest efficiency is the main objective of soil remediation technologies, the environmental side effects of the applied processes should be considered as important as the efficiency. In light of these, the main aim of this project was to increase Fenton treatment efficiency by using an environmental friendly solvent, ethyl lactate (EL). The project objectives included determining optimum levels for the reagents of Fenton reaction and desorption process such as hydrogen peroxide (H2O2) and EL, identifying the kinetic of TPH desorption and destruction of petroleum hydrocarbons by Fenton reaction in addition to analysing the effects of EL on these processes. Through desorption tests, EL/water solution demonstrated great ability to increase the removal efficiency and desorption of sorbed TPH. Desorption by EL/water solution consisted of a very fast desorption stage followed by a slow stage. After 30 min of desorption, the removal efficiency of TPH increased from 63% to 81% for EL=25% and EL=100%, respectively. The initial desorption rate for 25% and 100% were 1.625 mg/min and 3.368 mg/min, respectively. The results of batch experiments indicated that EL%=10% was the optimum value for the EL-modified Fenton reaction. After 4 h, an increase in H2O2 concentration from 0.1 M to 2 M at L/S=2 and EL=25% increased the removal efficiency of TPH from 68.41% to 90.21%. HA addition up to 150 mg/l was also studied. For fraction 1, adding HA led to an increase in removal efficiency while for fraction 2, only HA=150mg/l had higher removal efficiency than the HA=0 case and for fraction 3, addition of HA in the studied range could not increase the removal efficiency. A good compatibility of zero-valent iron nanomaterial with H2O2 was proved. Laboratory column experiments were finally carried out to remove petroleum hydrocarbons from diesel-contaminated soil with EL to reproduce the conditions of in-situ treatment. The remaining diesel in soil decreased by increasing H2O2 molarity from 0.1 M to 0.5 M whereas a further increase to 2 M led to an increase in remaining diesel in soil. The stability of H2O2 in EL has been observed which signifies good potential for in-situ applications. Overall, the project has demonstrated the feasibility of EL-modified Fenton reaction for the remediation of petroleum-contaminated soil
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